xfs: split up xfs_buf_allocate_memory

Based on a patch from Christoph Hellwig.

This splits out the heap allocation and page allocation portions of
the buffer memory allocation into two separate helper functions.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index 592800c8852f45f8794405e7b738ec2afb938c22..2e35d344a69be6c6728562e2d198e7ea78b46c03 100644 (file)
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -347,65 +347,55 @@ xfs_buf_free(
        kmem_cache_free(xfs_buf_zone, bp);
 }
 
-/*
- * Allocates all the pages for buffer in question and builds it's page list.
- */
-STATIC int
-xfs_buf_allocate_memory(
-       struct xfs_buf          *bp,
-       uint                    flags)
+static int
+xfs_buf_alloc_kmem(
+       struct xfs_buf  *bp,
+       size_t          size,
+       xfs_buf_flags_t flags)
 {
-       size_t                  size;
-       size_t                  nbytes, offset;
-       gfp_t                   gfp_mask = xb_to_gfp(flags);
-       unsigned short          page_count, i;
-       xfs_off_t               start, end;
-       int                     error;
-       xfs_km_flags_t          kmflag_mask = 0;
+       int             align_mask = xfs_buftarg_dma_alignment(bp->b_target);
+       xfs_km_flags_t  kmflag_mask = KM_NOFS;
 
-       /*
-        * assure zeroed buffer for non-read cases.
-        */
-       if (!(flags & XBF_READ)) {
+       /* Assure zeroed buffer for non-read cases. */
+       if (!(flags & XBF_READ))
                kmflag_mask |= KM_ZERO;
-               gfp_mask |= __GFP_ZERO;
-       }
 
-       /*
-        * for buffers that are contained within a single page, just allocate
-        * the memory from the heap - there's no need for the complexity of
-        * page arrays to keep allocation down to order 0.
-        */
-       size = BBTOB(bp->b_length);
-       if (size < PAGE_SIZE) {
-               int align_mask = xfs_buftarg_dma_alignment(bp->b_target);
-               bp->b_addr = kmem_alloc_io(size, align_mask,
-                                          KM_NOFS | kmflag_mask);
-               if (!bp->b_addr) {
-                       /* low memory - use alloc_page loop instead */
-                       goto use_alloc_page;
-               }
+       bp->b_addr = kmem_alloc_io(size, align_mask, kmflag_mask);
+       if (!bp->b_addr)
+               return -ENOMEM;
 
-               if (((unsigned long)(bp->b_addr + size - 1) & PAGE_MASK) !=
-                   ((unsigned long)bp->b_addr & PAGE_MASK)) {
-                       /* b_addr spans two pages - use alloc_page instead */
-                       kmem_free(bp->b_addr);
-                       bp->b_addr = NULL;
-                       goto use_alloc_page;
-               }
-               bp->b_offset = offset_in_page(bp->b_addr);
-               bp->b_pages = bp->b_page_array;
-               bp->b_pages[0] = kmem_to_page(bp->b_addr);
-               bp->b_page_count = 1;
-               bp->b_flags |= _XBF_KMEM;
-               return 0;
+       if (((unsigned long)(bp->b_addr + size - 1) & PAGE_MASK) !=
+           ((unsigned long)bp->b_addr & PAGE_MASK)) {
+               /* b_addr spans two pages - use alloc_page instead */
+               kmem_free(bp->b_addr);
+               bp->b_addr = NULL;
+               return -ENOMEM;
        }
+       bp->b_offset = offset_in_page(bp->b_addr);
+       bp->b_pages = bp->b_page_array;
+       bp->b_pages[0] = kmem_to_page(bp->b_addr);
+       bp->b_page_count = 1;
+       bp->b_flags |= _XBF_KMEM;
+       return 0;
+}
+
+static int
+xfs_buf_alloc_pages(
+       struct xfs_buf  *bp,
+       uint            page_count,
+       xfs_buf_flags_t flags)
+{
+       gfp_t           gfp_mask = xb_to_gfp(flags);
+       size_t          size;
+       size_t          offset;
+       size_t          nbytes;
+       int             i;
+       int             error;
+
+       /* Assure zeroed buffer for non-read cases. */
+       if (!(flags & XBF_READ))
+               gfp_mask |= __GFP_ZERO;
 
-use_alloc_page:
-       start = BBTOB(bp->b_maps[0].bm_bn) >> PAGE_SHIFT;
-       end = (BBTOB(bp->b_maps[0].bm_bn + bp->b_length) + PAGE_SIZE - 1)
-                                                               >> PAGE_SHIFT;
-       page_count = end - start;
        error = _xfs_buf_get_pages(bp, page_count);
        if (unlikely(error))
                return error;
@@ -458,6 +448,38 @@ out_free_pages:
        return error;
 }
 
+
+/*
+ * Allocates all the pages for buffer in question and builds it's page list.
+ */
+static int
+xfs_buf_allocate_memory(
+       struct xfs_buf          *bp,
+       uint                    flags)
+{
+       size_t                  size;
+       xfs_off_t               start, end;
+       int                     error;
+
+       /*
+        * For buffers that fit entirely within a single page, first attempt to
+        * allocate the memory from the heap to minimise memory usage. If we
+        * can't get heap memory for these small buffers, we fall back to using
+        * the page allocator.
+        */
+       size = BBTOB(bp->b_length);
+       if (size < PAGE_SIZE) {
+               error = xfs_buf_alloc_kmem(bp, size, flags);
+               if (!error)
+                       return 0;
+       }
+
+       start = BBTOB(bp->b_maps[0].bm_bn) >> PAGE_SHIFT;
+       end = (BBTOB(bp->b_maps[0].bm_bn + bp->b_length) + PAGE_SIZE - 1)
+                                                               >> PAGE_SHIFT;
+       return xfs_buf_alloc_pages(bp, end - start, flags);
+}
+
 /*
  *     Map buffer into kernel address-space if necessary.
  */